A wireless system may be implemented as a multiple-antenna receiver system (MARS), includes multiple-output (MO) communication systems. When a MO system has a single-antenna transmitter, it may be referred to as a single-input multiple-output (SIMO) system, and when the MO system has multiple-antenna transmitters, it may be referred to as a multiple-input multiple-output (MIMO) system. A MARS employs multiple antennas for performing spatial information processing. MARS are being incorporated into several industry standards including the IEEE 802.11n and WiMAX (IEEE 802.16) standards. MARS can also be used to improve performance of industry standards, such as Global Positioning Systems (GPS) and Digital Video Broadcasting (DVB), that do not require more than one antenna. MARS can also be used in multimode radios that can receive signals associated with multiple different systems.
The antennas of a MARS are adaptable for use in a manner that meets system performance objectives given application performance requirements, channel conditions, interference conditions, etc. Performance requirements may include specifications related to raw data rate, throughput, bit and/or packet error probability, average delay, delay jitter and/or system power consumption. MARS have the ability to adapt the way the receiver antennas are used as well as various transmission parameters such as transmit power, constellation size, channel coding scheme, frame length, etc.
Using multiple antennas in wireless transceivers may be advantageous. For example, system data rates can be increased through multiplexing. For another example, system performance can be improved by increasing link robustness through space-time coding, diversity-combining or more general beamforming. For another example, directional gain can be increased and/or interference can be reduced by steering the antenna beam in a given direction via beamsteering.
Although there are advantages to systems with multiple antennas at the transmitter and/or receiver, a disadvantage is the need for multiple RF transmit and/or receive signal paths, one path for each of the antennas. There are a number (N) of RF paths in a multiple-antenna transmitter or receiver employing N antennas, which generally leads to an N-fold increase in cost, size, and power consumption as compared to systems that do not employ multiple antennas such as SISO systems which have a single RF path at both the transmitter and receiver.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.